*This is just a theory I havent tried this*
I would think of making a ghost image of both drives. Then copying that ghost image in 2 seperate partitions on a single drive. Then come in with parition magic and turning the 2 partitions to 1. Again I have never heard of this so I am not sure it works but I don't see why not. Just don't have 2 working OS's on the same partition
I know can and have used with Norton Ghost taking a partition and create a new smaller partition and ghost it. Like if you have a 80 gig drive one partition but only 40 gigs of data on it. You can make a 40 gig partition image and telling Ghost to place all your data on it. In effect it optimizes/defrags that partition space and creates a smaller partition. Then you can put that ghost image anywhere you want. In fact you may be able to place those images on the same partition but I don't know how prudent that wouild be.
Of course there is always copying the files straight up from one drive to the other